NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Geocentric Orrery
From: Ken Muldrew
Date: 2026 Jul 7, 08:14 -0600
From: Ken Muldrew
Date: 2026 Jul 7, 08:14 -0600
Since you are printing the gears yourself, you can easily change the DP (diametral pitch) of the gears to get rid of the paired tooth count constraint. As long as paired gears have the same DP, there is no problem with meshing. This makes it a lot easier to get closer to the actual ratios.
Are you using pin-and-slot stacked gears to simulate elliptical orbits? That can make a big difference for the apparent position of a planet within a given revolution even if they catch up at the end of the revolution.
Ken Muldrew
On Thu, Jul 2, 2026 at 6:45 AM NavList Community <NavList@navlist.net> wrote:
Re: Geocentric Orrery
From: Trammell H
Date: 2026 Jul 2, 02:39 -0700While I could generate any arbitrary gear ratio using that sort of technique, it would require unique spacing for every gear combination, produces very large gears, and doesn't satisfy my additional constraint that the sum of the two gears must match the sums of all of the other gears in the systems. The last requirement comes from sharing the axles between all of the gear train stages. I do have flexibility in choosing this spacing, but am limited in the total number of teeth for manufacturing reasons, so I wrote a tool that exhaustively searches the spacings to find the ratios that are closest.
